Wheat straw and microbial inoculants have an additive effect on <scp> N <sub>2</sub> O </scp> emissions by changing microbial functional groups
Cheng Ji, Jidong Wang, Yuxiang Sun, Cong Xu, Jie Zhou, Yuehua Zhong, Yunwang Ning, Hui Zhang, Yongchun Zhang, Yinglong Chen
Abstract
Abstract Straw‐decomposing microbial inoculants (MIs) have been increasingly applied to straw‐amended soils. However, the interactive effects and underlying microbial mechanisms of straw and decomposing MIs on nitrous oxide (N 2 O) emissions remain unclear. Here, a pot experiment with an Aquic Inceptisol was conducted to determine soil N 2 O emissions and the abundance and composition of microbial functional genes under six amendments: wheat straw (W), Bacillus subtilis MI (B), Streptomyces rochei MI (S), a combination of straw and B. subtilis MI (WB), a combination of straw and S. rochei MI (WS), and a control without wheat straw or MI (C). Compared with the control, the amendments of straw, decomposing MIs, and their combinations decreased soil N 2 O emissions by 43%, 22–30%, and 46–60%, respectively. Mechanistically, the positive relationship between ammonia‐oxidizing bacteria (AOB) and soil potential nitrification rate (PNR), along with decreased AOB abundance (−36%) following straw and decomposing MI amendments, further suggested that AOB predominated soil nitrification and was responsible for the suppressed nitrification. In addition, straw amendment increased nirK gene abundance (by 48%) and potential denitrification rate (by 11%), while the increase in nosZI gene abundance (+25%) involved in N 2 O consumption contributed to the decrease in N 2 O emissions. Overall, the additive effect of straw and decomposing MIs on soil N 2 O emissions was associated with two amendment‐induced changes in the abundance and composition of AOB and straw‐stimulated the abundance of the nosZI gene. Our results revealed the potential for mitigating N 2 O emissions following the amendments of straw and MI by influencing soil N 2 O‐related microbial groups.